Nociceptive afferent topographical innervation of the heart and stomach

More than 50 million Americans suffer from chronic pain. Of those, 25 million live with daily chronic pain and lack effective and safe non-opioid options for pain management. In particular, the new incidence of chest pain is 15.5 per 1000 person-years, which is highly related to coronary heart disease and heart failure. In addition, the prevalence of chronic abdominal pain is around 22.9 per 1,000 person-years. A large percentage of abdominal pain is related to the gastrointestinal tract (GI). However, the anatomical and physiological mechanisms of peripheral nociceptive processes have not been well studied. In this study, we aim to perform a comprehensive anatomical mapping of pain-related neural circuitry in two visceral organs: heart (Aim 1) and stomach (Aim 2). Nociception, from these organs in mammals, is mainly mediated by sensory neurons in the spinal dorsal root ganglia (DRG) and to a lesser extent in the vagal nodose-jugular ganglion complex (for short: nodose ganglion, seen below). Previously, Dr. Powley’s group and Dr. Cheng’s group have studied vagal afferent and efferent as well as sympathetic efferent innervations of the heart and stomach, and their different types of terminal structures (taxonomy) in whole mounts of atria and the stomach. To do so, we used a combination of techniques, including tracer injections, anterograde tracing of axon distributions and terminal structures, and microscopic imaging. However, the study of specific nociceptive nerve topographical innervation in the heart and stomach is not well studied because such elegant, powerful, and challenging techniques above have not yet been well applied in the spinal DRG. In this study, we will inject different tracers into the DRG (left or right: C7-T5 for Heart; left or right: T6-T12 for Stomach) and into the vagal nodose ganglia (left or right: for both Heart and Stomach) for anterograde labeling of sensory nerve innervation. In addition, we will also use immunohistochemical (IHC) labeling of CGRP, SP, and TRPV1 (the three nociceptive nerve markers) in tracer-injected animals that will specifically identify the nociceptive afferent innervation of these organs from distinct origins (spinal, vagal, or left/right side). The topographical innervation map will be annotated and presented in the 3D reconstructed heart and stomach, and then their 3D scaffolds of these organs (Aim 3). We will also assess for organ specificity (nociceptive innervation that distinguishes the heart and stomach from each other), left or right sidedness of ganglia, and sex differences. Comprehensive and topographical mapping of nociceptive afferent innervation of these organs will substantially improve the understanding of physiological processes in relation to nociception. This mapping data will also aid to develop new selective interventional therapies/stimulations for visceral pain of these organs.